The technology relates to an SOC indicator that provides an indication of an SOC of a hybrid vehicle having an EV traveling mode.
An engine-electric motor hybrid vehicle (HV) includes an engine and a motor generator as power sources for traveling, allowing for motor assistance on occasions such as acceleration by using electric power. The electric power may be generated in association with use of a regeneration brake, etc. and charged in a battery.
In recent years, such a hybrid vehicle is further provided with a function of charging from an external power supply such as a domestic power supply and a commercial power supply, attaining expansion of a range of usability of an electric vehicle (EV) traveling mode that allows for traveling with sole use of the motor generator without using the engine. This type of hybrid vehicle has been spreading as a plug-in hybrid vehicle (PHEV).
The plug-in hybrid vehicle as mentioned above may include a secondary battery such as, but not limited to, a lithium ion battery and a nickel hydrogen battery, as power storage to accumulate electric power to be used in traveling.
In such a secondary battery, a ratio of residual electric power to chargeable electric power (total capacity) is called a state of charge (SOC).
In the plug-in hybrid vehicle, SOC control (charge and discharge control) of the battery may differ as follows between the EV traveling mode that involves traveling with sole use of the motor generator and an HV traveling mode with combined use of the engine and the motor generator.
In the EV traveling mode, in many cases, traveling may be started in a range of a relatively high SOC (almost full-charged); when the SOC decreases to the extent that continuation of the EV traveling mode becomes difficult, the EV traveling mode may be switched to the HV traveling mode.
In contrast, in the HV traveling mode, the SOC control may be targeted to a relatively low SOC state; within a relatively narrow SOC range, charge (e.g., regenerative power generation) and discharge (motor drive) may be repeated with high frequency.
The plug-in hybrid vehicle as mentioned above may include an SOC indicator (a battery residual capacity indicator) in order to present information on residual capacity of the battery to a driver.
As one example of existing techniques concerning such an SOC indicator, Japanese Patent (JP-B) No. 5223822 describes a residual capacity indicator that changes display colors of a bar graph in accordance with a first traveling mode and a second traveling mode. The first traveling mode gives priority to traveling with sole use of a motor. The second traveling mode involves use of an internal combustion engine and the generator.
JP-B No. 5223822 also provides a description that, in the display in the first traveling mode, the bar graph is color-divided at a position corresponding to residual capacity where the first traveling mode is switched to the second traveling mode.
Although the existing technique as mentioned above enables a grasp of a current SOC, it provides a driver with little information on a timing when the traveling mode will be returned to the EV traveling mode again, in a case of recovery of an SOC by charging such as regenerative power generation in traveling in the HV traveling mode. Hence, it is difficult to forecast switching of traveling modes.
Moreover, the HV traveling mode generally involves repetitive charge and discharge within a relatively narrower SOC range than that of the EV traveling mode. However, in the existing technique as mentioned above, an SOC indication is regularly performed on a scale of a full SOC range. Thus, charge and discharge in the HV traveling mode may only cause minute fluctuation within a narrow range in the SOC indication, leading to difficulties for a driver in grasping SOC transition.